Hi,
I'm David, and I want to start helping out with Geany development.
https://github.com/geany/geany/pull/36
I started by simplifying rstrip-whitespace.py. It seemed really complex. However, I'm not sure if you were doing anything special when removing trailing white space, because the code I made does simply that, not anything else.
Whether or not this patch gets approved, I'll keep on working and see how I can help. I know some Gtk, and even though I'm more used to its Vala bindings, I think I can do just fine with C and C++.